1. Gasymov, M.G., Levitan, B.M.: The inverse problem for a Dirac system. Dokl. Akad. Nauk SSSR 167, 967–970 (1966); English transl. in Soviet Math. Dokl. 7, 495–499 (1966)
2. Gasymov, M.G.: The inverse scattering problem for a system of Dirac equations of order 2n. Trudy Moscov. Mat. Obşç. 19, 41–112 (1968) (in Russian); English trans. Moscow Math. Soc. 19, 41–119 (1968)
3. Levitan, B.M., Sargsjan, I.S.: Sturm–Liouville and Dirac operators. Nauka, Moscow (1988); English transl., Kluwer, Dordrecht (1991)
4. Nizhnik, L.P., Vu, P.L.: An inverse scattering problem on the semi-axis with a nonselfadjoint potential matrix. Ukrain. Mat. Z. 26, 469–486 (1974) (in Russian); Ukrainian Math. J. 26, 384–398 (1975)
5. Sakhnovich, L.A.: Spectral Theory of Canonical Differential Systems. Method of Operator Identities. Birkhäuser, Basel (1999)